1. Field of the Invention
The present invention relates to a printed circuit board unit with a cooling device in general incorporated within an electronic apparatus such as a portable digital assistant (PDA), a notebook personal computer, and the like. In particular, the invention relates to a printed circuit board unit comprising a printed circuit board, a ventilation fan rotatable around the rotation axis intersecting the printed circuit board, and a fan housing accommodating the ventilation fan.
2. Description of the Prior Art
As disclosed in Japanese Patent Application Publication P2000-77877A, a so-called fan unit includes a fan housing accommodating a ventilation fan rotating around the rotation axis. When the ventilation fan rotates, air is allowed to flow in the centrifugal direction of the rotation axis. The fan housing serves to guide the air toward the outlet. The air is discharged out of the outlet. At the same time, air surrounding the fan housing is introduced into the fan housing through the inlet. The inlet is defined to face the surface of the printed circuit board. When the air is sucked into the fan housing, air is allowed to flow along the surface of the printed circuit board.
In general, a number of electronic components are mounted on the surface of the printed circuit board. The respective electronic components protrude from the surface of the printed circuit board, so that the electronic components hinder a smooth flow of the air. The turbulence in the air is supposed to constrain the ventilation fan from sucking the air into the fan housing. The suction quantity of the air may be reduced. The ventilation fan suffers from reduction in the cooling efficiency. As the printed circuit board gets thinner, the space is reduced between the fan housing and the surface of the printed circuit board. The cooling efficiency of the ventilation fan may still get deteriorated.